Our patient presented with an acute abdomen due to volvulus and perforation of the cyst. An acute presentation of these cysts has not been reported earlier, although Menon et al.,[1] suggested it to be a strong possibility. Another unique feature was the coexistence of the CIDC with a classic enteric duplication cyst, a finding reported only once earlier in the literature.[2] Norris et al.,[2] described a case with a long tubular duplication of the jejunum where the proximal 10 cm segment of the cyst shared a common seromuscular coat with the bowel wall, the middle 20 cm lay separately within the leaves of the mesentery, while the final 10 cm was suspended by its own mesentery and ended blindly. Thus, the duplication became more distant from the normal bowel as one progressed distally.[2] There was another large cystic enteric duplication within the mesenteric leaves and a large left-sided posterior mediastinal cyst connected by a pedicle to a smaller cyst within the diaphragm.

Many possible embryological mechanisms have been proposed for the origin of enteric duplications, namely partial or abortive twinning,[12] split notochord theory,[13] diverticular and canalisation defects,[14] and intrauterine vascular accidents.[15] Partial or abortive twinning can explain doubling or duplication anomalies of the head, upper alimentary tract, hindgut, and the lower genitourinary tract.[3,12] The split notochord theory proposes that abnormal separation of the notochord from the gut endoderm can cause dorsal enteric duplications or diverticulae[13] and this can account for the 15% of enteric duplications with associated vertebral defects.[16] The theory of aberrant luminal recanalization proposes to explain duplications in those portions of the gastrointestinal tract that go through the solid stage during embryonic development such as the esophagus, small intestine, and colon.[14] As such, no single mechanism can account for all the known variants of enteric duplications. Based on their study of 83 intestinal duplications, Li et al.,[17] classified them into two types based on the vascular supply to the duplication and the adjacent bowel. In this study, 91.6% patients with type 2 cysts had associated thoracic vertebral defects and Li et al.,[17] proposed that the embryology of type 2 cysts could be explained by the split notochord theory. Type 1 cysts could be explained by the theories of midline splitting of primordial tissue and persistence of fetal gut diverticula.[17]

Menon et al.,[1] suggested that their finding of a CIDC in the mesentery of the small bowel, supplied by blood vessels from the adjacent retroperitoneum rather than the mesenteric vessels, indicated that part of the embryonic gut had been sequestered during early embryonic life. Okamoto et al.,[4] also suggested that as the blood supply to their isolated gastric duplication cyst came from the adjacent retroperitoneum, the abnormality could have occurred at a relatively early gestational age by abnormal splitting of the notochord.[4]

The CIDC in our patient as well as in other reported cases[1,6,7,9,10] had a separate mesentery and can be considered as a variant of type 1 cysts according to Li et al.,[17] classification. The adjoining intramesenteric cyst can be classified as a type 2 cyst although the patient did not have any vertebral anomaly. However, it is difficult to explain the occurrence of two separate embryological mechanisms, as suggested by Li et al.,[17] to account for type 1 and type 2 cysts, occurring in the same patient. Steiner et al.,[6] proposed that the case reported by Norris et al.,[2] could represent an intermediate situation between a usual duplication and a completely isolated one with the proximal segment representing a classical duplication cyst and the distal segment a CIDC. This process might have been triggered by a vascular accident at the proximal end of the duplication resulting in a separated duplication cyst suspended by its own mesentery.[6] Although it is tempting to suggest that in our patient, a similar vascular accident could have resulted in complete separation of a segment from the classic duplication cyst resulting in the CIDC with its own leash of vessels, this theory cannot explain the finding that while the classic duplication cyst was lined by gastric mucosa, the adjacent CIDC was lined by intestinal mucosa. Significantly, in one of the cases reported by Norris et al.,[2] the intraabdominal duplication cysts were lined by intestinal mucosa while the mediastinal cysts were lined by gastric mucosa. Heterotopic gastric mucosa lining a CIDC has been reported,[6,7,9] while in one patient, a CIDC attached to the distal ileum was lined by respiratory epithelium.[16]